1. Field of the Invention
This invention relates to a machine for fitting and removing wheel tires for vehicles and equipped in particular with an automated wheel lifting arrangement.
2. The Prior Art
It is known that wheels for vehicles comprise a metal rim fitted with annular flanges along the perimeter adapted to house, as an adherent stop, the end portions, so-called “beads”, of an elastic tire.
The use is currently known of so-called “tire changing” machines for fitting and removing tires from and onto their relevant rims for carrying out maintenance, repair or replacement jobs.
Such tire changing machines comprise, generally, a framework adapted to support a clamping and rotating device for clamping and rotating the rim of a wheel onto/from which the tire must be fitted/removed and one or more tools for fitting and removing the tire.
It is known that the clamping and rotating device for clamping and rotating the rim are set at a given height off the ground in order to facilitate the access to the wheel by an operator during the tire removal/fitting operations.
Furthermore, the wheel is generally fixed to the clamping and rotating device around a substantially vertical axis.
This necessarily requires a preliminary operation to lift the wheel off the ground for positioning onto the clamping and rotating device, and later the repositioning of the wheel on the ground following the removal/fitting operation.
This lifting operation may require the tipping of the wheel for the horizontal positioning and with a vertical rotational axis on the clamping and rotating device, and later tipping to be repositioned on the ground.
The operations for lifting and positioning the wheel on the ground are generally done manually by the operator, who is consequently subjected to notable physical strain, and the operation may indeed have to be repeated many times in a day.
To prevent this problem, tire changing machines fitted with a lifting arrangement are known which tip and lift the wheel to the height of the clamping and rotating device in an automated manner (and, in the same way, reposition the wheel on the ground).
This lifting arrangement generally comprises a first horizontal framework that extends around the clamping and rotating device, and which moves along a vertical direction by means of the operation of a first actuator and which is intended to rest the wheel on it.
A second framework, fitted with protruding prongs, is hinged to one side of the first framework and can be rotated by means of the operation of a second actuator between a first lowered position, in which it is substantially vertical with the prongs arranged horizontally near the ground, and a second raised position, in which it is horizontal and coplanar to the first framework.
When using the lifting arrangement, the operator positions the wheel vertically on the second framework in the lowered position.
The first framework and the second framework hinged to it are then lifted by means of the operation of the first actuator and, following this, the second framework is moved to the raised position by means of the operation of the second actuator; in this raised position the wheel is horizontal (with a vertical rotation axis) and the first framework is positioned above the clamping and rotating device.
The operator then drags the wheel from the first framework onto the second framework, which may be fitted with idle rollers, and centres the rotation axis of the wheel with respect to the rotation axis of the clamping and rotating device below.
The first framework is then lowered by means of the first actuator to fix the wheel rim to the clamping and rotating device.
Following the tire removal/fitting operations, the rim is released from the clamping and rotating device and the combined action of the first and second framework, in the same way as described above, allows the wheel to be repositioned on the ground.
These known machines however have some difficulties.
The known lifting arrangements in fact oblige the operator to drag the wheel manually from the second framework to the first framework in order to position the wheel over the clamping and rotating device for centring and fixing. In the same way, the wheel must also be dragged by the operator manually from the first framework to the second framework to reposition the wheel on the ground.
Consequently, this also requires physical effort by the operator, and also constitutes a waste of time which greatly increases the overall wheel movement times towards/from the clamping and rotating device.
The main aim of this invention is to provide a machine for fitting and removing wheel tires for vehicles which assures faster and less tiring wheel movement operations.
A further object of this invention is to provide a machine for fitting and removing wheel tires which handles the wheel using a structurally and functionally simpler solution.
A further object of this invention is to provide a machine for fitting and removing tires which overcomes the aforementioned drawbacks of the prior art within a rational solution that is easy to use, efficient and cost-effective.